Windows update/defrag crashes

Hello,

I've had this problem for some time now. Originally it seemed to be caused by the disk defragmenter which I assumed was falling over on a bad block on the disk. What happens is the screen goes blank, and then the machine reboots.

I turned off the defrag from automatically running by changing the registry to prevent this.

However I also found there was a problem with windows updates. One update in particular (the ID I cannot now recall) would cause the same reset of the machine. Subsequently, I turned off automatic updates and manually installed updates except for the one causing this problem.

I ran chkdsk, but this also causes a reset of the machine! Even in safe mode.

I then turned off automatic updates for a while, and yesterday turned this on again (to download and install manually), however, the machine started resetting again. The TaskManager was showing wuauclt.exe and update.exe running at the point of failure, so I renamed these (!) and restarted - sure enough the problem has stopped.

So, I'm still unsure of what is causing the problem. If there is a bad block, unfortunately chkdsk cannot help me. If there is a bad driver, I'm not sure how I can safely track this down.

Any thoughts/help would be greatly appreciated.

Thanks,

Boris